1. Field of the Invention
The present invention relates to removal of ringing in the input unit of a pin electronics card used in semiconductor testing apparatus, output stage circuit inside the IC or LSI, or output unit of a device under test board (DUT board) used in semiconductor testing apparatus, and more particularly to a ringing preventive circuit for removing noise such as ringing from a transmission path in which an electric signal is transmitted.
2. Description of the Background Art
FIG. 25 is a conceptual diagram showing the connected state of the DUT board mounting a semiconductor device such as IC and LSI, and the input unit of a pin electronics card of a semiconductor testing apparatus, for testing a semiconductor apparatus such as IC and LSI. In FIG. 25, reference numeral 1 denotes an objective device to be tested such as IC and LSI, 2 is a DUT board for mounting the objective device 1, 3 is a holder such as socket and prober fixed on the DUT board 2 for holding and electrically connecting the objective device 1, 4 is a transmission path for transmitting an electric signal outputted from the output unit of the objective device 1, being connected to the objective device I in the holder 3, 5 is a connector connected to the transmission path 4 provided at the DUT board 2 side, 6 is a semiconductor testing apparatus for testing the objective device 1,7 is a pin electronics card provided in the semiconductor testing apparatus 6 and including a comparator or the like, and 8 is a connector provided in a pin electronics card 7 to be connected to the connector 5 of the DUT board 2.
The pin electronics card 7 of the semiconductor testing apparatus 6 is an input and output interface with the objective device 1, and has a significant influence on the test performance.
FIG. 26 is a circuit diagram showing the outline of the structure of the pin electronics card 7 of the semiconductor testing apparatus shown in FIG. 25. In FIG. 26, reference numeral K1 is a relay having one end connected to the connector 8 for making or breaking a connection between the one end and the other end in response to a control signal, 11 is a pin electronics comparator having an input terminal 11a connected to the other end of the relay K1, a terminal connected to a power source E5 to be provided with a reference voltage VHth, a terminal connected to a power source E6 to be provided with a reference voltage VLth, and an output terminal 11b for outputting the result of comparison of the voltage at the input terminal 11a with the reference voltages VHth, VLth, 12 is a pin electronics driver having an input terminal 12a for receiving a signal to be given to the objective device for testing, and an output terminal 12b connected to the other end of the relay K1, and 13 is a pin electronics control circuit for processing the signal to be given to the objective device from the semiconductor testing apparatus to give to the input terminal 12a of the pin electronics driver 12, processing the signal outputted from the output terminal 11b of the pin electronics comparator 11 to be taken into the semiconductor testing apparatus, and controlling to open or close the relay K1. Herein, it is supposed that reference voltage VHth  greater than reference voltage VLth.
The operation of the conventional semiconductor testing apparatus shown in FIG. 25 and FIG. 26 is described below. In particular, processing of the signal to be outputted from the objective device 1 is explained. In the pin electronics card 7, in order to process an input signal, the relay K1 is in ON (closed) state, so that the pin electronics comparator 11 may be connected between the connector 8 and pin electronics control circuit 13. The voltage VCO at the output terminal 11b of the pin electronics comparator 11 is, supposing the voltage at the input terminal 11a of the pin electronics comparator 11 to be VCi, VCO=VCL when VCi greater than VHth, VCO=VCL when VCi less than VLth, and VCO=VCH when VLth less than CCi less than VHth, where voltage VCL is the lower side logic level in the pin electronic control circuit 13, and voltage VCH is the higher side logic level in the pin electronics control circuit 13.
FIG. 27 is a waveform diagram showing the signal processed by the pin electronics card and the processing result in the pin electronics comparator. The waveform shown in (a) of FIG. 27 is a voltage waveform of an ideal electric signal suited to processing of the pin electronics comparator 11. Ideally, from the output circuit of the objective device 1 shown in FIG. 25, a signal having a waveform as shown in (a) of FIG. 27 is outputted, and passes through the transmission path 4, and a signal having the waveform shown in (a) of FIG. 27 is put into the connector 8 of the pin electronics card 7 in the semiconductor testing apparatus 6. From the connector 8 which is the input and output terminal of the pin electronics card, an ideal signal Vi is put in, and it is supplied into the pin electronics comparator 11 through the relay K1. Therefore, the voltage VCi at the input terminal 11a of the pin electronics comparator is ideally a signal Vi having the waveform shown in (a) of FIG. 27. At this time, the output impedance of the pin electronics driver 12 is supposed to be in high impedance state (hereinafter called Hi-Z state). Hence, ideally, the voltage waveform generated at the output terminal 11b by the action of the pin electronics comparator 11 is as shown in (b) of FIG. 27.
Actually, however, in the process of the waveform passing through the transmission path 4 and others, the signal having the voltage waveform as shown in FIG. 28 mixed with ringing and other noise due to inductance component and capacitance component of the transmission path 4, impedance mismatching of the transmission path 4, incoming noise mixed in the transmission path 4 and others is put into the pin electronics comparator 11.
FIG. 28 is a waveform diagram showing the signal processed in the pin electronics card and the processing result in the pin electronics comparator. When a signal having the waveform as shown in (a) of FIG. 28 is put into the pin electronics comparator 11, the pin electronics comparator 11 may sometimes malfunction. When the waveform shown in (a) of FIG. 28 is put into the pin electronics comparator 11, malfunction occurs in the portion crossing the voltage VHth in shaded region B in (a) of FIG. 28, and in the portion crossing the voltage VLth in shaded region D. When the signal having the waveform shown in (a) of FIG. 28 is put into the pin electronics comparator 11, the waveform appearing at the output terminal 11b of the pin electronics comparator 11 is as shown in (b) of FIG. 28. Shaded region E in (b) of FIG. 28 is the malfunctioning portion.
The pin electronics card is an interface between the objective device 1 and semiconductor testing apparatus 6, and the information indicated by the signal outputted from the objective device 1 must be accurately communicated to the semiconductor testing apparatus 6, but this object may not be achieved if malfunction occurs in the pin electronics comparator 11.
Incidentally, transmission of pulse signal or processing is not limited to the semiconductor testing apparatus alone, but such scene is often encountered in general semiconductor devices. FIG. 29 is a conceptual diagram showing part of the constitution of a general semiconductor device. In FIG. 29, reference numeral 14 is a semiconductor device, 15 is an output pin of the semiconductor device 14, 16 is an output buffer connected to the output pin 15 for giving an output signal to the output pin 15, 17 is a transmission path connected to the output buffer 16, and 18 is a circuit before an output stage for generating a circuit to be transmitted through the transmission path 17. The transmission path 17 may contain wiring of aluminum, polysilicon or the like, in the semiconductor device 14, and the output pin 15 may be a pad or the like.
A pulse signal having a certain waveform is outputted from the circuit before an output stage 18, and is transmitted to the output buffer 16 through the transmission path 17. It is further transmitted from the output buffer 16 having a low output impedance to the output pin 15, and is outputted outside the semiconductor device from the output pin 15. The waveform of the signal outputted from the circuit before an output stage 18 and the waveform transmitted to the output pin 15 should be ideally ringing-free waveform as shown in (a) of FIG. 27.
However, for example, when a signal having a waveform as shown in (a) of FIG. 27 is outputted from the circuit before an output stage 18, in the process of passing through the transmission path 17 or output buffer 16, it may be changed to a waveform having noise such as ringing, as shown in (a) of FIG. 28, due to inductance component in the transmission path 17, crosstalk noise from the peripheral circuit or the like, and may be transmitted to the output pin 15 in such form.
The conventional semiconductor testing apparatus, DUT board, and semiconductor device are thus constituted, and ringing or other nosie is caused in the process of the electric signal passing through the transmission paths 4, 17, and therefore when the signal mixed with ringing is processed, the circuit and others may malfunction, and accurate testing of semiconductor device or appropriate action of semiconductor device may not be realized.
A first aspect of the invention relates to a ringing preventive circuit comprising a buffer amplifier having an input terminal and an output terminal, a first comparator having a first input terminal connected to the output terminal of the buffer amplifier, a second input terminal provided with a first reference voltage, and an output terminal, for outputting a first control signal from the output terminal in response to a result of comparison between the voltages at the first and second input terminals, and a first current supply circuit having a first terminal connected to a first power source for supplying a first voltage, a second terminal connected to the input terminal of the buffer amplifier, and a control signal input terminal connected to the output terminal of first comparator, for controlling conduction and non-conduction of a current flowing from the first terminal to the second terminal by the first control signal.
A second aspect of the invention relates to a ringing preventive circuit of the first aspect, wherein the first current supply circuit comprises a constant current source having a first terminal and a second terminal connected to the first power source, and a second terminal, for supplying a specific current from the first terminal to the second terminal, and switch means having a first current electrode connected to the first terminal of the constant current source, a second current electrode connected to the input terminal of the buffer amplifier, and a control electrode connected to the second terminal of the first comparator, for controlling on/off of the current flowing between the first and second current electrodes in response to the signal given to the control electrode.
A third aspect of the invention relates to a ringing preventive circuit of the first aspect, wherein the first current supply circuit comprises switch means having a control electrode connected to the output terminal of the first comparator, a first current electrode provided with a second voltage relating to the first power source, and a second current electrode, for controlling conduction and non-conduction of a current flowing between the first and second current electrodes in response to the signal given to the control electrode, and a current mirror circuit connected to the first power source, having a first current output terminal connected to the second current electrode of the switch means, and a second current output terminal connected to the input terminal of the buffer amplifier, for outputting a first current from the first current output terminal and a second current from the second current output terminal, the second current in the second current output terminal is duplicated in said first current output terminal.
A fourth aspect of the invention relates to a ringing preventive circuit of the first aspect, further comprising a second comparator having a first input terminal connected to the output terminal of the buffer amplifier, a second input terminal provided with a second reference voltage, and an output terminal, for outputting a second control signal from the output terminal in response to a result of comparison between voltages of the first and second input terminals of the second comparator, and a second current supply circuit having a first terminal connected to a second power source for supplying a second voltage, a second terminal connected to the input terminal of the buffer amplifier, and a control signal input terminal connected to the output terminal of the buffer amplifier, for controlling conduction and non-conduction of a current flowing from the first terminal to the second terminal in response to the second control signal.
A fifth aspect of the invention relates to a ringing preventive circuit comprising a buffer amplifier having an input terminal and an output terminal, a first comparator having a first input terminal connected to the output terminal of the buffer amplifier, a second input terminal provided with a first reference voltage, and an output terminal, for outputting a first control signal from the output terminal in response to a result of comparison between voltages at the first an second input terminals, and a first current supply circuit having a first terminal connected to a first power source for supplying a first voltage, a second terminal connected to the input terminal of the buffer amplifier, a third terminal connected to the output terminal of the buffer amplifier, and a control signal input terminal connected to the output terminal of first comparator, for controlling conduction and non-conduction by the first control signal, and passing a current depending on the voltage of the third terminal from the first terminal to the second terminal.
A sixth aspect of the invention relates to a ringing preventive circuit of the fifth aspect, further comprising a second comparator having a first input terminal connected to the output terminal of the buffer amplifier, a second input terminal provided with a second reference voltage, and an output terminal, for outputting a control signal from the output terminal, in response to a result of comparison between voltages of the first and second input terminals, and a second current supply circuit having a first terminal connected to a second power source for supplying a second voltage, a second terminal connected to the input terminal of the buffer amplifier, a third terminal connected to the output terminal of the buffer amplifier, and a control signal input terminal connected to the output terminal of second comparator, for controlling conduction and non-conduction by the second control signal, and passing a current depending on the voltage of the third terminal from the first terminal to the second terminal.
A seventh aspect of the invention relates to a ringing preventive circuit of the fifth aspect, wherein the first current supply circuit comprises a differential amplifying circuit having a first power source terminal provided with a second voltage relating to the first power source, a first input terminal provided with a second reference voltage, a second input terminal connected to the output terminal of the buffer amplifier, and an output terminal, for amplifying the voltage difference between the input terminal and the second input terminal, and outputting on the basis of the second voltage, a transistor having a first current electrode connected to the output terminal of the differential amplifier circuit, a control electrode connected to the output terminal of the first comparator, and a second current electrode, and a current mirror circuit having a first current output terminal connected to the second current electrode of the transistor, a second current output terminal connected to the input terminal of the buffer amplifier, and a current input terminal connected to the first power source, for outputting a first current from the first current output terminal and a second current from the second current output terminal, the second current in the second current output terminal is duplicated in the first current output terminal.
An eighth aspect of the invention relates to a device under test board comprising a connector for connecting with a test head, a transmission path for transmitting a signal to the connector, holding means for holding an objective device and electrically connecting the transmission path and the objective device, and a ringing preventive circuit connected between the transmission path and the connector, for removing ringing of the signal transmitted through the transmission path, wherein the ringing preventive circuit comprises a buffer amplifier having an input terminal connected to the transmission path and an output terminal connected to the connector, a first comparator having a first input terminal connected to the output terminal of the buffer amplifier, a second input terminal provided with first reference voltage, and an output terminal, for outputting a control signal from the output terminal in response to a result of comparison between voltages of the first and second input terminals, and a first current supply circuit having a first terminal connected to a power source for supplying a supply voltage, a second terminal connected to the input terminal of the buffer amplifier, and a control signal input terminal connected to the output terminal of the first comparator, for controlling conduction and non-conduction of a current flowing from the first terminal to the second terminal in response to control signal.
A ninth aspect of the invention relates to a device under test board comprising a connector for connecting with a test head, a transmission path for transmitting a signal to the connector, holding means for holding an objective device and electrically connecting the transmission path and the objective device, and a ringing preventive circuit connected between the transmission path and the connector, for re-moving ringing of the signal transmitted through the transmission path, wherein the ringing preventive circuit comprises a buffer amplifier having an input terminal connected to the transmission path and an output terminal connected to the connector, a first comparator having a first input terminal connected to the output terminal of the buffer amplifier, a second input terminal provided with first reference voltage, and an output terminal, for outputting a control signal from the output terminal in response to a result of comparison between voltages of the first and second input terminals, and a first current supply circuit having a first terminal connected to a power source for supplying a supply voltage, a second terminal connected to the input terminal of the buffer amplifier, a third terminal connected to the output terminal of the buffer amplifier, and a control input terminal connected to the second output of the first comparator, for controlling on/off by the control signal, and passing a current depending on the voltage of the output terminal of the buffer amplifier from the first terminal to the second terminal.
A tenth aspect of the invention relates to a device under test board of the ninth aspect, further comprising a high impedance circuit inserted between the input terminal of the buffer amplifier and the transmission path, for setting the impedance of the transmission path as seen from the buffer amplifier higher than the impedance of the transmission path.
An eleventh aspect of the invention relates to a pin electronics card comprising a connector connected to a test board on which an objective device is mounted, an interface circuit having a signal input terminal for interfacing to use a signal entered from the signal input terminal as an input to the tester, and a ringing preventive circuit connected between the signal input terminal of the interface circuit and the connector, for removing ringing caused in a signal entered from the signal input terminal, wherein the ringing preventive circuit comprises a buffer amplifier having an input terminal connected to the connector, and an output terminal connected to the signal input terminal of the interface circuit, a first comparator having a first input terminal connected to the output terminal of the buffer amplifier, a second input terminal provided with a first reference voltage, and an output terminal, for outputting a control signal from the output terminal in response to a result of comparison between voltages of the first and second input terminals, and a first current supply circuit having a first terminal connected to a power source for supplying a supply voltage, a second terminal connected to the input terminal of the buffer amplifier, and a control signal input terminal connected to the second output terminal of the first comparator, for controlling conduction and non-conduction of a current flowing from the first terminal to the second terminal in response to the control signal.
A twelfth aspect of the invention relates to a pin electronics card comprising a connector connected to a test board on which an objective device is mounted, an interface circuit having a signal input terminal for interfacing to use a signal entered from the signal input terminal as an input to the tester, and a ringing preventive circuit connected between the signal input terminal of the interface circuit and the connector, for removing ringing caused in a signal entered from the signal input terminal, wherein the ringing preventive circuit comprises a buffer amplifier having an input terminal connected to the connector, and an output terminal connected to the signal input terminal, a first comparator having a first input terminal connected to the output terminal of the buffer amplifier, a second input terminal provided with a first reference voltage, and an output terminal, for outputting a control signal from the output terminal in response to a result of comparison between voltages of the first and second input terminals, and a first current supply circuit having a first terminal connected to a power source for supplying a supply voltage, a second terminal connected to the input terminal of the buffer amplifier, and a control signal input terminal connected to the output terminal of the first comparator, for controlling on/off by the control signal and passing a current from the first terminal to the second terminal depending on the voltage of the output terminal.
A thirteenth aspect of the invention relates to a pin electronics card of the twelfth aspect, further comprising a high impedance circuit inserted between the first input terminal of the buffer amplifier and the connector, for setting the impedance at the connector side as seen from the buffer amplifier hither than before insertion.
A fourteenth aspect of the invention relates to a semiconductor device having a ringing preventive circuit adjacent to an output pin for removing ringing of pulse signal outputted from an output stage, wherein said ringing preventive circuit comprises a buffer amplifier having an input terminal connected to the output stage, and an output terminal connected to the output pin, a first comparator having a first input terminal connected to the output terminal of the buffer amplifier, a second input terminal provided with a first reference voltage, and an output terminal, for outputting a control signal from the output terminal in response to a result of comparison between voltages of the first and second input terminals, and a first current supply circuit having a first terminal connected to a power source for supplying a supply voltage, a second terminal connected to the input terminal of the buffer amplifier, and a control signal input terminal connected to the output terminal of the first comparator, for controlling conduction and non-conduction of a current flowing from the first terminal to the second terminal by the control signal.
A fifteenth aspect of the invention relates to a semiconductor device having a ringing preventive circuit for removing ringing of pulse signal outputted from an output stage disposed near an output pin, wherein said ringing preventive circuit comprises a buffer amplifier having an input terminal connected to the connector, and an output terminal connected to the signal input terminal, a first comparator having a first input terminal connected to the output terminal of the buffer amplifier, a second input terminal provided with a first reference voltage, and an output terminal, for outputting a control signal from the output terminal in response to a result of comparison between voltages of the first and second input terminals, and a first current supply circuit having a first terminal connected to the power source, a second terminal connected to the input terminal of the buffer amplifier, a third terminal connected to the output terminal of the buffer amplifier, and a control signal input terminal connected to the output terminal of the first comparator, for controlling on/off by the control signal and passing a current from the first terminal to the second terminal depending on the voltage of the output terminal.
According to the first, eighth and eleventh aspects of the invention, the first comparator detects generation of ringing depending on whether the voltage of the output terminal of the buffer amplifier exceeds the first reference voltage or not. When ringing occurs, corresponding to the output of the first comparator, the first current supply circuit supplies a current to the input of the buffer amplifier, and the output of the buffer amplifier is restrained from exceeding the first reference voltage to increase the difference, thereby preventing ringing.
According to the second aspect of the invention, the constant current power source supplies a predetermined current to the switch means, and hence it is not necessary to adjust the element composing the first current supply circuit depending on the amplitude of the signal or magnitude of ringing.
It is not necessary to adjust the element composing the first current supply circuit, and hence handling of the ringing preventive circuit is easy.
According to the third aspect of the invention, the switch means has the first current electrode connected to the first power source, and the second current electrode to the first current output terminal of the current mirror circuit, and therefore the first and second current electrodes are free from effects of input and output of the buffer amplifier, and hence it is not necessary to adjust the element composing the first current supply circuit, and it is not influenced by, for example, the base line of the pulse entered in the input terminal of the buffer amplifier, and malfunction does not occur if the level of the signal of input and output of the buffer amplifier is shifted so that handling of the ringing preventive circuit may be easily performed.
According to the fourth aspect of the invention, the first and second comparators detect generation of ringing depending on whether the voltage of the output terminal of the buffer amplifier exceeds the first or second reference voltage or not. When ringing occurs, corresponding to the output of the first or second comparator, the first or second current supply circuit supplies a current to the input of the buffer amplifier, and the output of the buffer amplifier is restrained from exceeding the first and second reference voltage to increase the difference, so that ringing occurring in both rise and fall of a signal can be suppressed.
According to the fifth, ninth and twelfth aspects of the invention, the first comparator detects generation of ringing depending on whether the voltage of the output terminal of the buffer amplifier exceeds the first reference voltage or not. When ringing occurs, the first current supply circuit supplies a current corresponding to the output of the buffer amplifier to the input of the buffer amplifier, and the output of the buffer amplifier is restrained from exceeding the first reference voltage to increase the difference, so that ringing may be suppressed.
According to the sixth aspect of the invention, the first and second comparators detect generation of ringing depending on whether the voltage of the output terminal of the buffer amplifier exceeds the first or second reference voltage or not. When ringing occurs, the first and second current supply circuits supply a current corresponding to the output of the buffer amplifier to the input of the buffer amplifier, and the output of the buffer amplifier is restrained from exceeding the first and second reference voltages to increase the difference, so that ringing may be suppressed.
According to the seventh aspect of the invention, the first comparator detects generation of ringing depending on whether the voltage of the output terminal of the buffer amplifier exceeds the first reference voltage or not. When ringing occurs, the first current supply circuit supplies a current corresponding to the output of the buffer amplifier amplified by the differential amplifying circuit, to the input of the buffer amplifier, and the output of the buffer amplifier is restrained from exceeding the first reference voltage to increase the difference, so that ringing may be suppressed.
According to the tenth and thirteenth aspects of the invention, the first comparator detects generation of ringing depending on whether the voltage of the output terminal of the buffer amplifier exceeds the first reference voltage or not. When ringing occurs, the first current supply circuit supplies a current between the high impedance converting circuit and input terminal of the buffer amplifier, corresponding to the output of the first comparator, and the output of the buffer amplifier is restrained from exceeding the first reference voltage to increase the difference, and the current flowing when the first current supply circuit supplies the current can be decreased by the high impedance converting circuit.
According to the fourteenth aspect of the invention, the first comparator detects generation of ringing depending on whether the voltage of the output terminal of the buffer amplifier exceeds the first reference voltage or not. When ringing occurs in the pulse signal transmitted through a transmission path, the first current supply circuit supplies a current to the input terminal of the buffer amplifier, corresponding to the output of the first comparator, and the output of the buffer amplifier is restrained from exceeding the first reference voltage to increase the difference, and at this time, since the buffer amplifier is contained in the ringing preventive circuit, the buffer amplifier used in the output of the semiconductor may be omitted by adding the ringing preventive circuit. Accordingly, ringing can be suppressed by the ringing preventive circuit, while limiting expansion of the circuit scale by adding the ringing preventive circuit.
According to the fifteenth aspect of the invention, the first comparator detects generation of ringing depending on whether the voltage of the output terminal of the buffer amplifier exceeds the first reference voltage or not. When ringing occurs in the pulse signal transmitted through a transmission path, the first current supply circuit supplies a current to the input terminal of the buffer amplifier depending on the output of the buffer amplifier, corresponding to the output of the first comparator, and the output of the buffer amplifier is restrained from exceeding the first reference voltage to increase the difference, and at this time, since the buffer amplifier is contained in the ringing preventive circuit, the buffer amplifier used in the output of the semiconductor may be omitted by adding the ringing preventive circuit. Accordingly, the ringing can be suppressed by the ringing preventive circuit, while limiting expansion of the circuit scale by adding the ringing preventive circuit.
It is therefore an object of the present invention to provide a ringing preventive circuit capable of preventing malfunction in circuit and others in the subsequent stages by removing ringing at a specified position, if ringing or other noise should occur in the process of transmission of signal through a transmission path, in order to solve the problems in the prior art, and also to provide a pin electronics card of a semiconductor testing apparatus incorporating such ringing preventive circuit, DUT board incorporating a ringing preventive circuit, and a semiconductor device incorporating a ringing preventive circuit.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following description of the present invention when taken in conjunction with the accompanying drawings.